Ecosystems resilience assessment of forest and grassland subjected to ecological drought

• Construct a daily-scale index ESS that reflects multiple ecosystem service functions. • Integrate ESS and ecological water deficits to jointly identify ecological droughts. • Build ecosystem resilience curves for forests and grasslands via quantile regression. • Forests and grasslands resilience respond oppositely to rising drought intensity. Ecosystem resilience is essential for sustaining ecosystems in the face of increasingly extreme climate conditions. However, current research faces challenges in improving the accuracy of identifying ecological drought events, enhancing temporal resolution, and refining model fitting for resilience quantification. In this study, a novel, daily-scale Ecosystem Service Supply (ESS) index is introduced, integrating water yield, carbon storage, and habitat quality into a unified measure weighted by ecosystem service equivalency factors. Baiyangdian wetland in North China was chosen as the study area, where the ESS index and the Standardized Ecological Water Deficit Index (SEWDI) were combined to jointly identify ecological drought events that directly alter ecosystem functioning. To characterize post-drought recovery dynamics, Bayesian non-parametric quantile regression model is employed to construct resilience curves, which capture the relationship between drought intensity and ecosystem recovery time at multiple quantiles. The results reveal that forests exhibit greater resilience under mild drought conditions, while grasslands demonstrate superior recovery capacity during more severe droughts. Due to differences in ecosystem structure and vegetation characteristics, forest ecosystems experience a significant decline in resilience under extreme drought conditions. In contrast, grassland ecosystems generally maintain stable or even slightly improved recovery resilience. By improving the temporal resolution of ecosystem assessments and introducing a flexible method to quantify resilience trajectories, this approach offers valuable insights for evaluating drought resilience and guiding ecosystem management in water-limited environments.